Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Ordinary Shares Ionis Share Purchase Agreement	Ordinary Shares	Additional Paid-in Capital Ionis Share Purchase Agreement	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Ionis Share Purchase Agreement	Total
Beginning balance at Dec. 31, 2020		$ 266		$ 249,947	$ (3,193)	$ (151,560)		$ 95,460
Beginning balance (in shares) at Dec. 31, 2020		21,094,557
Increase (decrease) in shareholders' equity (deficit)
Issuance of ADSs upon exercise of share options		$ 1		283				284
Issuance of ADSs upon exercise of share options (in shares)		63,545
Issuance of ADSs, net of commissions and offering expenses		$ 33		58,742				58,775
Issuance of ADSs, net of commissions and offering expenses (in shares)		2,358,485
Share-based compensation expense				3,821				3,821
Foreign currency translation adjustment					(58)			(58)
Net loss						(16,191)		(16,191)
Ending balance at Mar. 31, 2021		$ 300		312,793	(3,251)	(167,751)		142,091
Ending balance (in shares) at Mar. 31, 2021		23,516,587
Beginning balance at Dec. 31, 2020		$ 266		249,947	(3,193)	(151,560)		95,460
Beginning balance (in shares) at Dec. 31, 2020		21,094,557
Increase (decrease) in shareholders' equity (deficit)
Net loss								(48,782)
Ending balance at Sep. 30, 2021		$ 329		374,029	(3,193)	(200,342)		170,823
Ending balance (in shares) at Sep. 30, 2021		25,595,326
Beginning balance at Mar. 31, 2021		$ 300		312,793	(3,251)	(167,751)		142,091
Beginning balance (in shares) at Mar. 31, 2021		23,516,587
Increase (decrease) in shareholders' equity (deficit)
Issuance of ADSs upon exercise of share options		$ 2		1,573				1,575
Issuance of ADSs upon exercise of share options (in shares)		125,666
Issuance of ADSs, net of commissions and offering expenses		$ 7		13,970				13,977
Issuance of ADSs, net of commissions and offering expenses (in shares)		482,299
Share-based compensation expense				2,575				2,575
Foreign currency translation adjustment					(255)			(255)
Net loss						(17,913)		(17,913)
Ending balance at Jun. 30, 2021		$ 309		330,911	(3,506)	(185,664)		142,050
Ending balance (in shares) at Jun. 30, 2021		24,124,552
Increase (decrease) in shareholders' equity (deficit)
Issuance of ADSs upon exercise of share options		$ 4		3,045				3,049
Issuance of ADSs upon exercise of share options (in shares)		257,389
Issuance of ADSs, net of commissions and offering expenses	$ 4	$ 12	$ 7,554	29,831			$ 7,558	29,843
Issuance of ADSs, net of commissions and offering expenses (in shares)	282,485	930,900
Share-based compensation expense				2,688				2,688
Foreign currency translation adjustment					313			313
Net loss						(14,678)		(14,678)
Ending balance at Sep. 30, 2021		$ 329		374,029	(3,193)	(200,342)		170,823
Ending balance (in shares) at Sep. 30, 2021		25,595,326
Beginning balance at Dec. 31, 2021		$ 384		567,637	(3,388)	(218,379)		$ 346,254
Beginning balance (in shares) at Dec. 31, 2021		29,579,364						29,579,364
Increase (decrease) in shareholders' equity (deficit)
Issuance of ADSs upon exercise of share options		$ 1		449				$ 450
Issuance of ADSs upon exercise of share options (in shares)		30,074
Issuance of ADSs upon vesting of restricted share units (in shares)		35,000
Share-based compensation expense				10,198				10,198
Foreign currency translation adjustment					920			920
Net loss						(27,564)		(27,564)
Ending balance at Mar. 31, 2022		$ 385		578,284	(2,468)	(245,943)		330,258
Ending balance (in shares) at Mar. 31, 2022		29,644,438
Beginning balance at Dec. 31, 2021		$ 384		567,637	(3,388)	(218,379)		$ 346,254
Beginning balance (in shares) at Dec. 31, 2021		29,579,364						29,579,364
Increase (decrease) in shareholders' equity (deficit)
Foreign currency translation adjustment								$ 3,916
Net loss								(82,739)
Ending balance at Sep. 30, 2022		$ 385		589,679	528	(301,118)		$ 289,474
Ending balance (in shares) at Sep. 30, 2022		29,678,431						29,678,431
Beginning balance at Mar. 31, 2022		$ 385		578,284	(2,468)	(245,943)		$ 330,258
Beginning balance (in shares) at Mar. 31, 2022		29,644,438
Increase (decrease) in shareholders' equity (deficit)
Issuance of ADSs upon exercise of share options				195				195
Issuance of ADSs upon exercise of share options (in shares)		21,879
Share-based compensation expense				5,673				5,673
Foreign currency translation adjustment					2,094			2,094
Net loss						(26,828)		(26,828)
Ending balance at Jun. 30, 2022		$ 385		584,152	(374)	(272,771)		311,392
Ending balance (in shares) at Jun. 30, 2022		29,666,317
Increase (decrease) in shareholders' equity (deficit)
Issuance of ADSs upon exercise of share options				159				159
Issuance of ADSs upon exercise of share options (in shares)		12,114
Share-based compensation expense				5,368				5,368
Foreign currency translation adjustment					902			902
Net loss						(28,347)		(28,347)
Ending balance at Sep. 30, 2022		$ 385		$ 589,679	$ 528	$ (301,118)		$ 289,474
Ending balance (in shares) at Sep. 30, 2022		29,678,431						29,678,431